6 replies to this topic

[rsk]

To maintain minimum recirculation flow through BFP during all operational conditions arrangement of recirculation line with orifice from pump discharge to deareator is being chosen.
The inputs are from pump curve the max pressure at req minimum flow of 525m3/hr is 75kg/cm2 & deareator pressure is 5kg/cm2 please elaborate the broad steps i should follow for sizing of orifice & line.
regards

[JoeWong]

rsk,

The minimum flow @ pressure from pump curve are 525m3/hr is 75kg/cm2 (@ specific density) respective.

1. Base on 525 m3/h, suggest maximum velocity of 3 m/s, size the recycle line.

2. Base on 525 m3/h , above estimated recycle line size and along the line downstream of recycle line, determine the back pressure (Pd) at the downstream of restriction orifice (RO)

3. Base on 525 m3/h, from to pump and to RO upstream, determine the pressure at RO upstream (Pu)

4. Calculate the RO size base on 525 m3/h, Differential pressure (DP) = Pd-Pu, incompressible fluid.
Check your result with the calculator here.

Good luck.

[katmar]

The calculation procedure given by Joe is the right way to size an RO, but I must ask whether an RO is the right tool for a job. If you are "wasting" 525m3/h at 75 kg/cm2 continuously through a recycle line that is an awful lot of pumping energy being wasted.

If 525m3/h is your MINIMUM flow then I guess your BEP will be around 2500 m3/h? It would be unusual to pump this quantity at 75 kg/cm2 with a single pump. Also, that is one massive boiler you've got there. Either you have a decimal point position problem, or you need to re-evaluate your control strategy.

[fallah]

The calculation procedure given by Joe is the right way to size an RO, but I must ask whether an RO is the right tool for a job. If you are "wasting" 525m3/h at 75 kg/cm2 continuously through a recycle line that is an awful lot of pumping energy being wasted.

If 525m3/h is your MINIMUM flow then I guess your BEP will be around 2500 m3/h? It would be unusual to pump this quantity at 75 kg/cm2 with a single pump. Also, that is one massive boiler you've got there. Either you have a decimal point position problem, or you need to re-evaluate your control strategy.

1-Single pump but several stages.
2-Considering fixed RO might be because of limitations for applying other min. flow control methods due to special characteristics of pump curve,lack of possibility for RO installation in discharge line,...rsk will explain the reasons.

Regards

[rsk]

Thanks for replying
the scheme for recirculation is with contol valve in recirculation line. the flow control loop measuring total flow maitains minimum forward flow.
I just wanted to know the sizing approach for the alternative.

[wil ma]

Hi,

May be you can use a "schroeder-valve"

http://www.offshore-...es/h-schroeder/

Kind regards

[JoeWong]

If this is Boiler Feed Water service, i have seen many times ARC or "Schroeder" valve being used.